Shown here in a chemical reaction with copper and iron, Prussian blue is used in medicine because of its ability to detect iron and its demonstrated biological inactivity.
An implantable film created by researchers at the Massachusetts Institute of Technology enables users to control drug delivery. The film disintegrates when voltage is applied across its surface, thereby releasing the drug.
The researchers used nanoparticles of a pigment called Prussian blue—an inorganic iron hexacyanoferrate compound—to make the film and a chemical called dextran sulphate to represent the drug in their prototype. Prussian blue is often used as a stain to detect iron in biopsy specimens. It is also safe for ingestion.
The film is made from alternating layers of two materials: the negatively charged pigment and a positively charged drug molecule, or a neutral drug wrapped in a positively charged molecule. The result is a film that is typically about 150 nm thick.
The electrical signal can be remotely administered using radio signals or other techniques. When an electrical charge is applied to the film, the pigment Prussian blue loses its negative charge, which causes the film to disintegrate, releasing the drug. The amount of drug delivered and the timing of the dose can be precisely controlled by turning the voltage on and off.
The film can carry discrete packets of drugs that can be released separately, which could be beneficial for chemotherapy. The team is now working on loading the film with different cancer drugs. Eventually, devices could be designed to sense when a dose is needed and automatically deliver drugs. For example, a film could release chemotherapy agents if a tumor starts to regrow, or deliver insulin if a diabetic patient has high blood sugar.